The present invention is directed to a method and device for adjusting a reference system of a pre-programmable beam deflection system of a process-controlled, computer-assisted laser device functioning in a giant pulse mode with respect to the position of the inscription field of a part to be processed particularly a silicon wafer. The method of adjusting utilizes a plurality of program search motions of a laser beam, which is scanning the part and is from a laser operating in a continuous wave mode, and senses light signals with photoelements to create position signals which are utilized to calculate the precise position of the part with respect to the reference system and corrects the coordinates of the reference system to match the precise position.
A method of adjusting a reference system of a preprogrammable beam deflection system of a process-controlled, computer-assisted laser device functioning in a giant pulse mode is disclosed in German LP No. 23 35 517. In this known system, the search motion of a laser beam, which is operating in a continuous wave mode or operation, scans the part and is programmed in such a manner that the reference marks disposed within the part to be processed can be found. In addition, photoelements or light detection elements are disposed above the work surface in such a manner that they can detect the reflected laser beam. Thus, one photoelement is allocated to each reference mark and each photoelement triggers a signal as soon as the reflected laser beam impinges upon it. A precondition for this, however, is that the part to be processed is positioned in such a manner that only a relatively slight correction motion is required for the system.
Laser devices, such as disclosed in U.S. Pat. No. 3,902,037, are also known for processing and labeling in which a measuring beam of a measuring laser is faded into the beam path of the giant pulse mode processing laser. This, however, presumes that the workpiece or part to be processed is precisely aligned regarding its processing location relative to the reference system of the processing laser. The alignment of the workpiece not only requires a considerable time but also presumes expensive devices such as an x-y work table.
To overcome these problems, German OS No. 26 24 121 proposes that the shape and size of a known workpiece surface is scanned by means of a laser measuring beam, the light of the laser measuring beam that is reflected from the surface of the workpiece is employed with the assistance of photodiodes for the identification of the position of the workpiece within the work field of the processing laser in such a manner that the potential coordinates of the workpiece surface can be identified relative to the center point coordinates of the work surface of the processing laser. With the assistance of a process control computer, the center point coordinates of the workpiece surface in the work field are calculated from these signals and subsequently the control program for the processing laser is transformed to the center coordinates of the workpiece surface.